Our research represents an interdisciplinary approach to fundamental problems in cellular immunology. The major goals are: 1. to develop new methods for the fractionation of lymphoid cells according to the specificity of their surface receptors using the method of fiber fractionation and use this approach to provide a quantitative description of clonal selection; 2. to study the ontogeny of antigen-binding cells during fetal development and to study cell-cell interactions in tissue culture; 3. to map the lymphocyte surface in terms of Ig receptors, lectin receptors, histocompatibility antigens, and other distinctive markers; 4. to determine the number, distribution, and anchorage of surface receptors and characterize molecules that modulate receptor mobility to provide a basis for describing receptor-receptor and receptor-cytoplasmic interactions; 5. to analyze the biochemical mechanims by which lymphocytes are triggered to mature and divide by mitogens and specific antigens, including a description of the population dynamics, receptor-cytoplasmic interactions, and surface-nuclear signals; 6. to isolate and characterize the light and heavy chains of the major histocompatibility antigens in terms of amino acid sequence and to relate these sequences to the genetics and evolution of these antigens; 7. to determine possible functions of histocompatibility antigens in terms of immune surveillance against virally-infected and tumor cells; 8. to determine the amino acid sequences and three-dimensional structures of a variety of lectins, lymphocyte products, and immunoglobulins by microchemical methods and by X-ray crystallography and to study the interactions of lectins with lymphocytes by electron microscopy. BIBLIOGRAPHIC REFERENCES: Schrader, J.W. and Edelman, G.M. Participation of the H-2 antigens of tumor cells in their lysis by syngeneic T cells. J. Exp. Med. 143, 601-614 (1976). Edelman, G.M. Surface modulation in cell recognition and cell growth. Science 192, 218-226 (1976).